/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  package org.apache.maven.internal.impl.di;
  
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.LinkedList;
  import java.util.Map;
  import java.util.function.Supplier;
  
  import org.apache.maven.api.annotations.Nonnull;
  import org.apache.maven.di.Key;
  import org.apache.maven.di.Scope;
  import org.apache.maven.di.impl.DIException;
  
  /**
   * MojoExecutionScope
   */
  public class MojoExecutionScope implements Scope {
  
      protected static final class ScopeState {
          private final Map<Key<?>, Supplier<?>> seeded = new HashMap<>();
  
          private final Map<Key<?>, Object> provided = new HashMap<>();
  
          public <T> void seed(Class<T> clazz, Supplier<T> value) {
              seeded.put(Key.of(clazz), value);
          }
  
          public Collection<Object> provided() {
              return provided.values();
          }
      }
  
      private final ThreadLocal<LinkedList<ScopeState>> values = new ThreadLocal<>();
  
      public MojoExecutionScope() {}
  
      public static <T> Supplier<T> seededKeySupplier(Class<? extends T> clazz) {
          return () -> {
              throw new IllegalStateException(
                      "No instance of " + clazz.getName() + " is bound to the mojo execution scope.");
          };
      }
  
      public void enter() {
          LinkedList<ScopeState> stack = values.get();
          if (stack == null) {
              stack = new LinkedList<>();
              values.set(stack);
          }
          stack.addFirst(new ScopeState());
      }
  
      protected ScopeState getScopeState() {
          LinkedList<ScopeState> stack = values.get();
          if (stack == null || stack.isEmpty()) {
              throw new IllegalStateException();
          }
          return stack.getFirst();
      }
  
      public void exit() {
          final LinkedList<ScopeState> stack = values.get();
          if (stack == null || stack.isEmpty()) {
              throw new IllegalStateException();
          }
          stack.removeFirst();
          if (stack.isEmpty()) {
              values.remove();
          }
      }
  
      public <T> void seed(Class<T> clazz, Supplier<T> value) {
          getScopeState().seed(clazz, value);
      }
  
      public <T> void seed(Class<T> clazz, final T value) {
          seed(clazz, (Supplier<T>) () -> value);
      }
  
      @SuppressWarnings("unchecked")
      @Nonnull
     public <T> Supplier<T> scope(@Nonnull Key<T> key, @Nonnull Supplier<T> unscoped) {
         return () -> {
             LinkedList<ScopeState> stack = values.get();
             if (stack == null || stack.isEmpty()) {
                 throw new DIException("Cannot access " + key + " outside of a scoping block");
             }
 
             ScopeState state = stack.getFirst();
 
             Supplier<?> seeded = state.seeded.get(key);
 
             if (seeded != null) {
                 return (T) seeded.get();
             }
 
             T provided = (T) state.provided.get(key);
             if (provided == null && unscoped != null) {
                 provided = unscoped.get();
                 state.provided.put(key, provided);
             }
 
             return provided;
         };
     }
 }